Diaphragm pump

ABSTRACT

A pump ( 10 ) comprising an inlet ( 12 ), an outlet ( 14 ) and a pumping chamber ( 16 ) between the inlet ( 10 ) and the outlet ( 12 ). The pumping chamber ( 16 ) has first and second opposed interior pumping chamber surfaces ( 18, 20 ) extending from the inlet ( 12 ) to the outlet ( 14 ) in a pumping direction (PD). The pump ( 10 ) also has a flexible diaphragm ( 22 ) between the first and second pumping chamber surfaces ( 18, 20 ) which is adapted to substantially sealingly separate the first and second pumping chamber surfaces ( 18, 20 ) from one another. The diaphragm ( 22 ) has first and second layers ( 24, 26 ) adjacent the first and second pumping chamber surfaces ( 18, 20 ) respectively. A means ( 38 ) is also provided which induces substantially sinusoidal motion in the diaphragm ( 22 ) in the pumping direction (PD) without inducing relative movement between the diaphragm ( 22 ) and the pumping chamber ( 16 ) in the pumping direction (PD). The amplitude of the sinusoidal motion is approximately equal to the distance between the first and second pumping chamber surfaces ( 18, 20 ) in a direction normal to the pumping direction (PD) minus the distance between the sides of the diaphragm first and second layers ( 24, 26 ) adjacent the pumping chamber surfaces ( 18, 20 ). The length of the pumping chamber ( 16 ) in the pumping direction (PD) is greater than or equal to one wavelength of the sinusoidally shaped diaphragm ( 22 ) and the motion inducing means ( 38 ) is, at least in the region of the diaphragm ( 22 ) adjacent the first and second pumping chamber surfaces ( 18, 20 ), disposed within the first and second layers ( 24, 26 ) of the diaphragm ( 22 ).

TECHNICAL FIELD

[0001] The present invention relates to a pump and particularly to apump which utilises a travelling wave to drive a fluid.

BACKGROUND OF THE INVENTION

[0002] Known travelling wave pumps either used internal mechanicalmoving parts to drive a fluid or enclose the driven fluid within aflexible envelope in which cavities are formed and progressed byapplication of external mechanical moving parts. An example of theformer are known as MONO (Trade Mark) pumps, which suffer from thedisadvantage that the internal mechanical moving parts are exposed topossible damage whilst pumping corrosive fluids or from any abrasivesolids suspended within the pumped fluids. An example of the latter areperistaltic pumps, which suffer from the disadvantage that the pressurethat can be contained by the flexing envelope is limited whichcorrespondingly limits the pumping pressure the pumps are able togenerate.

OBJECT OF THE INVENTION

[0003] It is an object of the present invention to substantiallyovercome or at least ameliorate the disadvantages of the prior art pumpsdiscussed above.

SUMMARY OF THE INVENTION

[0004] Accordingly, in a first aspect, the present invention provides apump comprising:

[0005] an inlet;

[0006] an outlet;

[0007] a pumping chamber between the inlet and the outlet, the pumpingchamber having first and second opposed interior pumping chambersurfaces extending from the inlet to the outlet in a pumping direction;

[0008] a flexible diaphragm between the first and second pumping chambersurfaces and adapted to substantially sealingly separate the first andsecond pumping chamber surfaces from one another, the diaphragm havingfirst and second outer layers disposed adjacent the first and secondpumping chamber surfaces respectively; and

[0009] means to induce substantially sinusoidal motion in the diaphragmin the pumping direction without inducing relative movement between thediaphragm and the pumping chamber in the pumping direction, theamplitude of the sinusoidal motion being approximately equal to thedistance between the first and second pumping chamber surfaces in adirection normal to the pumping direction minus the distance between thesides of the diaphragm first and second layers adjacent the pumpingchamber surfaces,

[0010] wherein the length of the pumping chamber in the pumpingdirection is greater than or equal to one wavelength of saidsinusoidally shaped diaphragm and said motion inducing means is, atleast in the region of the diaphragm adjacent the first and secondpumping chamber surfaces, disposed within the first and second layers ofthe diaphragm.

[0011] The motion inducing means preferably includes at least onerotatable shaft extending in the pumping direction with a helicalsection in the region of the first and second pumping chamber surfaces,the helical section being disposed between the first and second layersof the diaphragm, the periphery of the helical section travelling alonga circular path about its rotational axis.

[0012] The motion inducing means desirably includes two said rotatableshafts extending in the pumping direction, said shafts being spacedapart in said diaphragm and arranged for synchronous, and mostpreferably counter, rotation relative to one another.

[0013] The pump desirably has two opposed pump casing halves each havinga recess therein respectively defining one of said two said pumpingchamber surfaces.

[0014] In one form, when viewed in the pumping direction, the recessesare of a curved concave shape. In this form, the diaphragm includeslongitudinal edges that extend in the pumping direction and thediaphragm is sealingly clamped between said casing halves along saidedges.

[0015] In another form, when viewed in the pumping direction, therecesses are of a rectangular concave shape. In this form, the diaphragmincludes longitudinal edges that extend in the pumping direction adaptedto sealingly slide along opposed walls of the pumping chamber.

[0016] The pump preferably also includes at least one resilient axialbeam within said diaphragm extending in a direction parallel to saidpumping direction, said beam(s) compressed along its/their length(s)into a substantially sinusoidal configuration and adapted to deformadjacent regions of said diaphragm to said sinusoidal configuration.More preferably, the pump includes at least one pair of said resilientaxial beams within said diaphragm, one of said beams in said pair(s)disposed between the motion inducing means and said first diaphragmlayer and the other of said beams in said pair(s) disposed between themotion inducing means and said second diaphragm layer.

[0017] The pump can also include at least one resilient lateral beamwithin said diaphragm extending in a direction normal to said pumpingdirection, said lateral beam(s) biased to a substantially flatconfiguration and adapted to deform adjacent regions of said diaphragmto a curved configuration replicating an adjacent said pumping chambersurface when the beam(s) is/are driven towards said pumping chambersurface by said motion inducing means. More preferably, the pump caninclude a plurality of said lateral beams disposed in a parallel andspaced apart relationship between said pump inlet and outlet.

[0018] A spacing means is preferably provided within said diaphragmwhich is adapted to maintain said first and second layers of thediaphragm a constant distance apart.

[0019] The pump preferably also includes a drive means adjacent one ofthe inlet or outlet and a bearing journal adjacent the other of saidinlet or outlet, the drive means adapted to rotate one end of said shaftand the journal adapted to support the other end of said shaft. Morepreferably, the drive means is adjacent the inlet and the journal isadjacent the outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Preferred embodiment of the invention will now be described, byway of examples only, with reference to the accompanying drawings, inwhich:

[0021]FIG. 1 is a cross sectional side view of a first embodiment of apump according to the invention;

[0022]FIG. 2 is a cross sectional end view of the pump shown in FIG. 1;

[0023]FIG. 3 is a cross sectional end view of a second embodiment of apump according to the invention;

[0024]FIG. 4 is a cross sectional end view of a third embodiment of apump according to the invention;

[0025]FIG. 5 is a cross sectional end view of a fourth embodiment of apump according to the invention;

[0026]FIGS. 6A and 6B are bending moment diagrams of a lateral beamemployed in fifth and sixth embodiments of pumps according to theinvention;

[0027]FIGS. 7A to 7I are schematic end views of the fifth embodiment ofa pump according to the invention employing lateral beams shown in FIG.6B at varying positions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028]FIG. 1 shows a cross sectional side view of a first embodiment ofa pump 10 in accordance with the invention. The pump 10 comprises aninlet 12, an outlet 14 and a pumping chamber 16 therebetween. Thepumping chamber 16 has first and second opposed interior pumping chambersurfaces 18 and 20 respectively, that extend from the inlet 12 to theoutlet 14 in a pumping direction indicated by arrow PD.

[0029] A flexible diaphragm 22, preferably formed from a strong plasticmaterial, is disposed between the first and second pumping chambersurfaces 18 and 20. The diaphragm 22 is adapted to substantiallysealingly separate the first and second pumping chamber surfaces 18 and20 from one another, in the region of the pumping chamber 16. Thediaphragm 22 has first and second layers 24 and 26 respectively whichare respectively adjacent the first and second pumping chamber surfaces18 and 20 respectively.

[0030] The sealed separation of the first and second pumping chambersurfaces 18 and 20 by the diaphragm 22 is best described with referenceto FIG. 2, which is a cross sectional end view of the pump 10 shown inFIG. 1. More particularly, FIG. 2 shows that the pump 10 has a metalpump casing formed from two opposed pump casing halves 28 and 30 thateach have a curved concave recess therein respectively defining the twopumping chamber surfaces 18 and 20. When viewed in the pumpingdirection, the curved recesses give the pumping chamber 16 asubstantially elliptical shape.

[0031] The diaphragm 22 includes longitudinal edges 32 and 34 extendingin the pumping direction which are sealingly clamped, by bolts 35,between the casing halves 28 and 30. In this way, the first and secondpumping chamber surfaces 18, 20 are sealed from one another. Also bestseen in FIG. 2 is that the majority of the interior of the diaphragm 22between the edges 32 and 34 is filled with a flexible spacing material36, preferably a plastic concertina-like insert, which is adapted tomaintain the first and second layers 24 and 26 of the diaphragm 22 apredetermined constant distance apart.

[0032] Returning to FIG. 1, the pump 10 also includes a means to inducesubstantially sinusoidal motion in the diaphragm 22 in the pumpingdirection without inducing relative movement between the diaphragm 22and the pumping chamber 16 in the pumping direction. In the embodimentshown, the motion inducing means is in the form of a metal rotatableshaft 38 that is helical in shape in the region of the pumping chamber16. The shaft 38 also includes one end in the inlet 12 which isconnected to a rotational drive source, such as an electric motor (notshown), by a sealed right angled gear drive 40. The other end of theshaft 38 also includes a cylindrical section which is supported in asealed bearing journal 42.

[0033] The helical section of the shaft 38 forces the flexible diaphragminto a substantially sinusoidal shape having an amplitude approximatelyequal to the distance between the first and second pumping chambersurfaces 18 and 20 in a direction normal to the pumping direction, minusthe distance between the exterior sides of the first and seconddiaphragm layers 24 and 26 that are adjacent the first and secondpumping chamber surfaces 18 and 20. The wavelength of the sinusoidallyshaped diaphragm 22 is approximately equal to the length of the pumpingchamber 16 such that a sealed volume between the peaks of the diaphragmis formed, as indicated by the hatched region 44.

[0034] In use, rotation of the shaft 38 causes the peaks and troughs ofthe diaphragm 22 to progressively move along the pumping chambersurfaces 18, 20 respectively, thereby driving the sealed volume 44 fromthe inlet 12 to the outlet 14 and inducing pumping of fluid containedtherein from the inlet 12 to the outlet 14.

[0035] Generally speaking, the motion of the helical portion of theshaft 38 is transferred to the diaphragm 22 along the length of thehelical portion. More particularly, the motion is transferred via a pairof resilient axial beams, which will be described in more detail below.

[0036]FIG. 2 shows a cross section through the pump 10 along line 2-2.As the helical portion of the shaft 38 is rotated the portion of theshaft shown travels, in the plane of FIG. 2, along a circular pathindicated by dashed lines 48, thereby driving the diaphragm 22 adjacentthat portion that from a first position (FIG. 2) where the first layer24 of the diaphragm 22 is forced against the first pumping chambersurface 18 to an opposed second position in which the second layer 26 ofthe diaphragm 22 is forced against the second pumping chamber surface 20then the first position and so on. This reciprocal movement will also beevident from FIGS. 6A to 6I, which will be described below.

[0037] As mentioned above, the diaphragm 22 also includes first andsecond resilient axial beams 52 and 54 which extend along the diaphragmin the pumping direction adjacent the region of the diaphragm 22occupied by the helical portion of the shaft 38. The beams 52,54 arepreferably formed from a stiff resilient material such as a hard plasticor spring steel. When straight, the beams 52, 54 are longer than astraight line between the inlet 12 and the outlet 14 of the pump 10.When they are compressed to fit between the inlet 12 and outlet 14 theydeform to a substantially sinusoidal configuration adjacent the helicalportion of the shaft 38. The resilient nature of the compressed beams 52and 54 serves to assist the diaphragm 22 in maintaining its sinusoidalshape and therefore a continual sealing front against the first andsecond pumping chamber surfaces 18, 20.

[0038]FIG. 3 is an end cross sectional view of a second embodiment of apump 60 according to the invention. The pump 60 is similar to the pump10 and like reference numerals have been used to denote like features.The primary difference between the pumps 60 and 10 is that the pump 60includes bearings, in the form of five roller sleeves 62 around theshaft 38, to provide a rolling action, and thus reduce friction, betweenthe shaft 38 and the axial beams 52 and 54.

[0039]FIG. 4 is an end cross sectional view of a third embodiment of apump 70 according to the invention. The pump 70 is similar to the pump10 and like reference numerals have been used to denote like features.The primary difference between the pumps 70 and 10 is that the pump 70includes a pair of synchronous counter-rotating shafts 38 disposed inthe diaphragm 22 in a spaced apart relationship and two correspondingpairs of axial beams 52 and 54. The increased number of drive shafts 38further enhances the sealing between the diaphragm 22 and the first andsecond pumping chamber surfaces 18 and 20, thereby allowing higherpumping pressures to be generated.

[0040]FIG. 5 is a cross sectional end view of a fourth embodiment of apump 80 according to the invention. Again, like reference numerals usedin describing the pump 10 will denote like features with respect to thepump 80. The casing halves 28 and 30 of the pump 80 have concaverecesses that are rectangular in shape that together define a pumpingchamber 16 of substantially rectangular cross section, when viewed inthe pumping direction.

[0041] In the pump 80, the sealing between the first and second pumpingchamber surfaces 18 and 20 by the diaphragm 22 is accomplished by thelongitudinal edges 32 and 34 of the diaphragm maintaining a slidingsealing relationship with the side walls 82 and 84 of the pumpingchamber 16.

[0042]FIGS. 6A and 6B will be used to describe the effect of applying abending moment M upon a beam B. Generally speaking, when a bendingmoment M is imposed upon a beam B it flexes to produce a curve having aradii of curvature at points along its length which depend on thebending moment applied at that point. If the otherwise unrestrainedflexing of the beam B is restrained by a surface, a reaction force isproduced at those points of restraint.

[0043]FIG. 6A shows a bending moment M applied by rotating the beam B inopposite senses at each of its ends. As a result, the unrestrainedradius of curvature R will be constant along the length of the beam. Asillustrated in FIG. 5B restraint of the flexing of the beam B by asurface S, in which the local radius of curvature increases at eachsuccessive point towards the centre from each side, introduces a localdistributed reaction force per unit length of arc p between therestrained beam and the surface. The rate of change of that increase inrate of curvature R with change of position towards the centres fromeach side determines the distribution of the reaction force p betweenthe flexed beam B and the surface S.

[0044] However, the bending moment need not be applied only at the endsof the beam B. In a fifth embodiment of the invention, which is avariation of the first and second embodiments, lateral resilient beamsare included in the diaphragm 22. A bending moment will arise in a beamfrom a force being applied to its centre, thereby pushing the beamagainst the surface S, as shown by arrow A in FIG. 6B. A forceequivalent to A is generated by the shaft 38 shown in FIGS. 1 and 2 andFIG. 3.

[0045] A sixth embodiment of the invention (not shown) is a variation ofthe third embodiment. A bending moment will arise from a force beingapplied to two points equally distant from the centre of the beam whichpush the beam against the surface S, as shown by the arrows B in FIG.6B. Such forces B are generated by the two shafts 38 shown in FIG. 4.

[0046]FIGS. 7A to 7I show schematic cross sectional end views of thefifth embodiment of a pump 90 utilising first and second resilientlateral beams 92 and 94, which are of similar construction to the axialbeams 52,54.

[0047] The beam 92 is disposed between the first surface 24 of thediaphragm 22 and the axial beam 52. The beam 94 is disposed between thesecond surface 26 of the diaphragm 22 and the axial beam 54. FIGS. 7A to7I show the position of a point of the helical portion of the shaft 38in 45° increments as it completes one rotation about path 48. Thelateral beams 92 and 94 are respectively and reciprocally driven towardsthe first and second pumping chamber surfaces 18 and 20 and, as thebeams have a natural tendency to be in a substantially flatconfiguration, when they are pressed against the pumping chambersurfaces 18 and 20 they assist in forcing the portion of the diaphragm22 adjacent the beam 92 or 94 to deform to a curved configurationreplicating the adjacent pumping chamber surface 18 or 20. This improvessealing therebetween which again improves pumping pressure.

[0048] The primary advantage of the invention is it provides atravelling wave pump in which none of the mechanical moving parts usedto drive the pump are exposed to contact with the fluids being pumped orany material suspended therein. This improves the mechanical life of thecomponents generally and also provides the pump with particularsuitability for transporting of abrasive, corrosive or otherwisecomponent damaging material. Also, as the mechanical moving parts aresealed within the diaphragm then the diaphragm can be filled with alubricant for the mechanical moving parts that will remain separatedfrom the material being pumped.

[0049] Although the invention has been described with reference to thepreferred embodiments, it will be appreciated by the skilled in the artthat the invention can be embodied in many other forms. As an example,whilst embodiments have shown the use of one or two drive shafts andfive bearings, any number of shafts/bearings can be placed within thediaphragm. Further, although the embodiment showed a sinusoidally shapeddiaphragm with a wavelength equal to the length of the pumping chamber,the diaphragm and pumping chamber can be configured such that multiplewavelengths of diaphragm are disposed within the pumping chamber. Also,whilst the embodiments have been described with a pumping direction froman inlet towards the outlet it should also be appreciated that reversingthe direction of rotation of the shaft also reverses the pumpingdirection and hence the inlet becomes the outlet and the outlet becomesthe inlet. Finally, the gear drive need not be a sealed unit inside theinlet of the pump. An alternative is an external drive mechanismconnected to the shaft through a sealed opening in the pump casing.

1. A pump comprising: an inlet; an outlet; a pumping chamber between theinlet and the outlet, the pumping chamber having first and secondopposed interior pumping chamber surfaces extending from the inlet tothe outlet in a pumping direction; a flexible diaphragm between thefirst and second pumping chamber surfaces and adapted to substantiallysealingly separate the first and second pumping chamber surfaces fromone another, the diaphragm having first and second outer layers disposedadjacent the first and second pumping chamber surfaces respectively; andmeans to induce substantially sinusoidal motion in the diaphragm in thepumping direction without inducing relative movement between thediaphragm and the pumping chamber in the pumping direction, theamplitude of the sinusoidal motion being approximately equal to thedistance between the first and second pumping chamber surfaces in adirection normal to the pumping direction minus the distance between thesides of the diaphragm first and second layers adjacent the pumpingchamber surfaces, wherein the length of the pumping chamber in thepumping direction is greater than or equal to one wavelength of saidsinusoidally shaped diaphragm and said motion inducing means is, atleast in the region of the diaphragm adjacent the first and secondpumping chamber surfaces, disposed within the first and second layers ofthe diaphragm.
 2. The pump claimed in claim 1, wherein the motioninducing means includes at least one rotatable shaft extending in thepumping direction with a helical section in the region of the first andsecond pumping chamber surfaces, the helical section being disposedbetween the first and second layers of the diaphragm, the periphery ofthe helical section travelling along a circular path about itsrotational axis.
 3. The pump claimed in claim 1 or 2, wherein the motioninducing means includes two said rotatable shafts extending in thepumping direction, said shafts being spaced apart in said diaphragm andarranged for synchronous rotation relative to one another.
 4. The pumpclaimed in any one of the preceding claims, further including twoopposed pump casing halves each having a recess therein respectivelydefining one of said two said pumping chamber surfaces.
 5. The pumpclaimed in claim 4, wherein, when viewed in the pumping direction, therecesses are of a curved concave shape.
 6. The pump claimed in claim 5,wherein said diaphragm includes longitudinal edges that extend in thepumping direction and the diaphragm is sealingly clamped between saidcasing halves along said edges.
 7. The pump claimed in any one of claims1 to 4, wherein, when viewed in the pumping direction, the recesses areof a concave substantially rectangular shape.
 8. The pump claimed inclaim 7, wherein said diaphragm includes longitudinal edges that extendin the pumping direction adapted to sealingly slide along opposed wallsof the pumping chamber.
 9. The pump as claimed in any one of thepreceding claims, further including at least one resilient axial beamwithin said diaphragm extending in a direction parallel to said pumpingdirection, said axial beam(s) compressed along its/their length(s) intoa substantially sinusoidal configuration and adapted to deform adjacentregions of said diaphragm to said sinusoidal configuration.
 10. The pumpas claimed in claim 9, including at least one pair of said resilientaxial beams within said diaphragm, one of said beams in said pair(s)disposed between the motion inducing means and said first diaphragmlayer and the other of said beams in said pair(s) disposed between themotion inducing means and said second diaphragm layer.
 11. The pump asclaimed in any one of the preceding claims, further including at leastone resilient lateral beam within said diaphragm extending in adirection normal to said pumping direction, said lateral beam(s) biasedto a substantially flat configuration and adapted to deform adjacentregions of said diaphragm to a curved configuration replicating anadjacent said pumping chamber surface when the beam(s) is/are driventowards said pumping chamber surface by said motion inducing means. 12.The pump as claimed in claim 11, further including a plurality of saidlateral beams disposed in a parallel and spaced apart relationshipbetween said pump inlet and outlet.
 13. The pump as claimed in any oneof the preceding claims, further including spacing means within saiddiaphragm adapted to maintain said first and second layers of thediaphragm a constant distance apart.
 14. The pump as claimed in any oneof claims 2 to 13, further including a drive means adjacent one of theinlet or outlet and a bearing journal adjacent the other of said inletor outlet, the drive means adapted to rotate one end of said shaft andthe journal adapted to support the other end of said shaft.
 15. The pumpas claimed in claim 14, wherein said drive means is adjacent the inletand said journal is adjacent the outlet.